The present invention relates to an industrial truck having an arrangement for increasing the braking force of at least one wheel of the industrial truck relative to a driving surface on which the industrial truck is driven, the industrial truck comprising a chassis which is supported on wheels which have substantially no suspension, and which is driven and braked by a sprung drive-wheel arranged between two of the support wheels and a load-carrying device which can be raised and lowered relative to the chassis by means of a hydraulic lifting arrangement intended therefor, and in which trucks there is arranged between the chassis and the drive-wheel a spring assembly which is operative in applying a spring force to the drive-wheel in a direction towards the driving surface on which the truck stands.
Industrial trucks of this kind are used for transporting goods-laden pallets within, for example, industrial premises. The trucks may be intended solely for low lifts, or for both low and high lifts, when handling stock in pallet racks or the like. Normally, the supporting wheels are completely without suspension, whereas the drive-wheel is pressed against the driving surface with a given spring force, in order to hold the wheel in contact with the driving surface when meeting irregularities therein. The magnitude of this spring force is determined by the condition that the chassis must rest on all support wheels, even when being driven with no load, so that stability remains the same, i.e. the spring force must not be of such magnitude that the drive-wheel lifts the support wheels from the driving surface. This means, however, that the surface engagement pressure of the drive-wheel remains unaltered when switching from light to heavier loads, which results in disadvantageous skidding and sliding tendencies, and above all substantially lengthens the braking distance as a result of the increase in kinetic energy. Since trucks of this kind have become progressively lighter in weight in relation to their load carrying capacity and can be driven at high speeds, the aforementioned drawback has reached greater proportions in recent years.